As you probably know already, the Ubuntu Linux developers discussed last year the removal of support for 32-bit PowerPC systems, which means that starting with Ubuntu 17.04 (Zesty Zapus) there won’t be any ISO images available to let you install Ubuntu or any of the official flavors on the PowerPC (PPC) 32-bit architecture. At the moment, Ubuntu MATE and Lubuntu appear to be the only official flavors to offer PowerPC install mediums, but it looks like the Lubuntu team will stop developing them after the Feature Freeze development stage of Lubuntu 17.04, which starts next week on February 16, 2017.